Indoor fishfarm with raised tank

ABSTRACT

An indoor fish tank has a of walls and bottoms interconnected to define distinct fish holding, sedimentation and bioreactor sections. Water flows out of the bioreactor section into the top of the fish holding section, and then from the bottom of the fish holding section into the sedimentation section. A frame structure with braces connected with the tank walls and bottoms supports the tank on a ground support, with at least the bottom of the fish holding section raised above the ground surface.

BACKGROUND OF THE INVENTION

The present invention relates to an indoor fish tank, comprising wallsand floors which define a tank container having a fish holding section,a sedimentation section connected via at least one opening to the fishholding section in such a way that water from a region close to thegroundflows from the fish holding section into the sedimentationsection, and a bioreactor section which is connected via at least oneopening to the fish holding section in such a way that water from aregion close to the upper surface flows out of the bioreactor sectioninto the fish holding section.

Overfishing and environmental influences have led to a stagnation offishery yields worldwide, and to a decline in yields for some species offish. One promising approach for preserving natural fish stocks is tobreed fish in aquacultures. A distinction is made here inbetweenextensive and intensive aquacultures, wherein intensive aquacultures areable to produce higher yields than extensive aquacultures due toartificial feeding.

Fish ponds, launder systems and net pen aquacultures are aquaculturemethods that are currently used to significant commercial extent.However, each of these forms of aquaculture exhibit specific problemscaused by factors relating to approval regulations, on the one hand, andrelating, on the other hand, to the need for a continuous supply offresh water (in the case of launder systems), and to the continuousremoval of fish feces and food remnants into the natural surroundings(in the case of net pen aquaculture).

For many years, work has therefore been carried out to developaquacultures that are designed as recirculation systems. Theserecirculation systems are also referred to as indoor fish farms, and aredistinguished by fish being bred within a closed water circulationsystem. It should be understood in this regard that fish tanks of suchrecirculation systems are preferably erected inside buildings, althoughthis indoor fish breeding technique in such recirculation systems couldalso be used outdoors.

A fish tank for fish breeding, suitable for intensive fish aquaculturein the form of a recirculation system, is known from German patent DE195 21 037, the entire disclosure of which is incorporated herein byreference. From a technical perspective, the bioreactor section and thesedimentation section are considered important elements of such a fishtank. In the sedimentation section, solids are sedimented and removedfrom circulation, which necessitates feeding a small amount of freshwater as compensation into the (semi-)closed circuit. In the reactorsection, oxygen is supplied by means of a finely distributed aerationsystem to the breeding water, and the organic substances are decomposedintensively by micro-organisms therein.

Fish tanks of this kind are basically well-suited for a recirculationaquaculture. However, there is a need for improvements to be made toenable more efficient management of these fish tanks in larger fishfarms, and in particular to enable maintenance work to be carried outmore easily on the fish tank.

There is also a need for fish tanks that can be installed in a morecost-efficient manner than prior art fish tanks.

Finally, there is a need for indoor fish tanks which make it easier toharvest the fish.

SUMMARY OF THE INVENTION

These and other problems in the prior art are solved, according to afirst aspect of the present invention, wherein an indoor fish tank ofthe kind initially specified is provided with a frame structure whichdefines a ground contact area on which the frame structure rests, andwhich is connected to the walls and/or floor of the fish tank in such away that at least the bottom of the fish holding section, and preferablythe bottoms of the sedimentation section and the reactor section, aredisposed above the ground contact area.

With the aid of the frame structure, the indoor fish tank according tothe invention is raised in its entirety onto stands that permitessential regions, or all regions filled with water to be above thefloor of the building on which the frame structure is erected. As aconsequence, the need for costly excavation work and foundation workwhen installing the fish tank is obviated. The external accessibility ofthe fish tank is also improved to the extent that all essential outerwall regions of the fish tank are accessible for maintenance and servicework, due to its being disposed in a raised position, whichsubstantially improves operations and the repairing of any damage. Moreparticularly, raising the fish tank on stands allows an indoor fish farmto be disposed in an existing building, without the ground inside havingto be modified, excavated or adapted in any such way. Instead, theinventive fish tank, including the frame structure accommodating it, canbe erected on the floor of an existing building, thus substantiallyreducing the installation costs.

It should be understood in this regard that the fish tanks according tothe present invention are breeding tanks. These typically and preferablyhave a total volume of 15-23 m3, preferably 20 m3. Of that total, 4-6 m3is typically for the bioreactor section, in particular 5 m3, 8-12 m3 forthe fish holding section, in particular 10 m3, and 3-5 m3 for thesedimentation section, in particular 4 m3.

It should be understood in this regard that not all bottom regions ofthe fish tank according to the present invention need necessarily beabove the ground contact area of the frame structure. As can be seenfrom DE 195 21 037 A1, one advantageous structure for a fish tank canspecifically be one in which both the sedimentation section and thereactor section of the fish tank have bottom regions which are lowerthan the fish holding section. In certain applications, it may thereforebe advantageous to sink at least one lower segment of the sedimentationsection and/or of the reactor section into a depression or hollow, andto dispose only the bottom of the fish holding section above the groundcontact area or congruent therewith. What is preferred, however, is thatthe entire tank be disposed above the ground contact area, so that noregions of the tank extend into the ground on which the frame structureis standing.

According to a first preferred embodiment of the present invention, theframe structure consists of a plurality of braces or struts which restagainst the outer surfaces of the walls and bottoms of the tankcontainer and support the same against the static pressure of the volumeof water held in the tank container. This embodiment gives the framestructure a twin functional benefit, firstly in that the frame structureabsorbs the static pressure produced inside the tank by the pressure ofthe water, thus allows the tank to have a thinner walls and amaterial-saving design, which for its part does not have to bedimensioned to withstand the static pressure on its own. Secondly, theframe structure is used to bear the weight force of the fish tank atleast partially, and preferably entirely, and to support it on theground. To this end, a particularly preferred embodiment is one in whichthe frame structure has at least horizontal and vertical braces, andpreferably diagonal bracing as well.

According to another preferred embodiment of the present invention, aclosable opening is provided in a wall bounding the fish holdingsection, which preferably has a connector for attaching one end of aharvesting line located outside the tank container. Such an openingallows the water inside the fish tank, or at least inside the fishholding section of the fish tank, to be drained under the influence ofgravity, and hence without the aid of pumps or the like. Moreparticularly, however, such an opening can be used to simplifyharvesting of the fish tank, in that the fish are removed along with thewater through the opening, and if necessary, through the harvesting lineinto a separate container by the force of gravity, and in this wayconcentrate in a separate harvesting container. The water flowing intothe harvesting container can be recycled to the fish tank, leaving thefish behind.

It is also preferred that the bioreactor section, the fish holdingsection and the sedimentation section are arranged fluidically in seriesin that order, and that the fish holding section is preferably disposedgeometrically between the bioreactor section and the sedimentationsection. In this way, a flow of water through the fish tank is achievedin a technically and geometrically advantageous manner, which permitsdirect delivery of fresh water into the fish holding section from thereactor section, and indirect removal of solids from the holding sectioninto the sedimentation section, as a result of which the water qualityin the aquaculture is optimized. The structure of a fish tank of suchconstruction is particularly suitable for an arrangement having aplurality of fish tanks arranged in a water circuit.

The present invention can be developed or, according to a furtheraspect, embodied in a fish tank of the kind initially specified, whereina flow shaft is disposed between the bioreactor section and the fishholding section, with the flow shaft being separated from the bioreactorsection by a first bulkhead partition which has an opening in its topportion, and which is separated from the fish holding section by asecond bulkhead partition which has an opening below the upper portion,preferably in the lower portion, the lower boundary edge of said openingpreferably being level with the bottom of the fish holding section.According to this aspect of the present invention, a particularlybeneficial flow of water through the fish tank, in particular throughthe fish holding section, is achieved. It is generally advantageous, onthe one hand, when the bioreactor section has an outlet opening locatednear the surface of the water in the fish tank for the water which flowsthrough the bioreactor section, in order that a flow of water throughthe entire bioreactor section is achieved by means of the air which isinjected into its bottom region. On the other hand, it has been shownthat it is desirable to improve the removal of sediment from the fishholding section through an opening in the bottom region of the fishholding section, between the fish holding section and the sedimentationsection. This is achieved by means of the second bulkhead partition, inthat the water discharged from the bioreactor section into the fishholding section is not discharged in the upper region, but rather into alower region of the fish holding section. This causes a flow of waternear the bottom in the fish holding section in the direction of thesedimentation section. This flow of water near the bottom of the fishholding section is beneficial and carries sediment efficiently into thesedimentation section, especially when the lower limit of both theopening in the second bulkhead partition and the opening between thefish holding section and the sedimentation section are level with thebottom surface of the fish holding section.

According to another aspect of the present invention, an indoor fishtank arrangement is provided, comprising:

-   -   at least one pair of the above described fish tanks, arranged in        relation to each other such that the facing walls of the fish        holding sections of the two fish tanks define a space between        the fish tanks, and    -   a maintenance walkway disposed in said space at such a height        that a person standing on the maintenance walkway can reach into        the fish holding section from above.

Another aspect of the present invention relates to a fish farm of anysize, comprising a plurality of fish tanks having the inventivestructure described in the foregoing. At least two fish tanks arearranged as a pair, and in the space between these fish tanks amaintenance walkway is provided which allows a user to performmaintenance and service work on the fish tanks.

The fish tank arrangement according to the present invention can bedeveloped by providing a plurality of fish tank pairs arranged relativeto each other such that the spaces between the fish tank pairs form amaintenance alleyway, and by providing a maintenance gangway formed bythe maintenance walkways. Due to this advantageous arrangement, a userof the fish tank arrangement can efficiently perform maintenance workand service work on a plurality of fish tank pairs that are arrangedsuch that a first row is formed by one fish tank of each pair, and asecond row is formed by the respective other fish tank of each pair. Forthis purpose, a maintenance gangway is positioned between the two rowsformed by the pairs of fish tanks, with the gangway providing anelevated place to stand and perform maintenance and service work. Itshould be understood in this regard that the maintenance gangway, likethe aforementioned maintenance walkway, is preferably fixed stationarilyor movably on the frame structure of the fish tanks.

It is further preferred when the fish tank arrangement according to thepresent invention includes a harvesting wagon which is mounted to bedisplaceable in the axial direction of the maintenance gangway, and hasa container for receiving fish, said container preferably beingconnectable by means of a harvesting line to the harvesting opening of afish tank. Such a harvesting wagon, according to the present invention,greatly facilitates the use of the inventive fish tank arrangement andmakes more efficient operation possible. The harvesting wagon, beingdesigned to be longitudinally displaceable, can be moved along the fishtanks, and in this way, can be moved to a particular fish tank which isto be harvested. The harvesting operation itself can be carried out inthe conventional manner, using dip nets or the like, or with the fishbeing filled directly into the container of the harvesting wagon via ashort pathway. In one particularly preferred embodiment of the presentinvention, a direct connection is formed between the fish holdingsection and the container of the harvesting wagon, for example via aharvesting line that can be connected to a matching opening in the tank,thus achieving a flow of fish from the fish tank into the container ofthe harvesting wagon, preferably under the force of gravity. It shouldbe understood in this regard that the harvesting wagon preferablyincludes a mechanism for conveying at least part of the water flowingout of the container back into the fish tank, for example by a pump,with an appropriate device being provided to retain the fish in thecontainer of the harvesting wagon.

According to yet another preferred embodiment of the present invention,the indoor fish tank arrangement is developed by a harvesting wagonwhich is mounted to be displaceable on rails in the axial direction ofthe maintenance gangway, with the rails preferably being mounted on theframe structure of the fish tank. Such mounting can be carried outspecifically by rollers that are disposed on the harvesting wagon andthat run on the rails, and allow the harvesting wagon to be movedquietly and effortlessly. More particularly, the rails may be attachedto the frame structure in order to achieve an overall more compact andmaterial-saving structure for the inventive arrangement. It should beunderstood in this regard that the rails may be arranged on either sideof the path of travel of the harvesting wagon, and for this purpose, maybe arranged and attached to frame structures of adjacent rows of fishtanks.

In one special embodiment of the variant with the harvesting wagon, theharvesting wagon is mounted to be displaceable in the region formed bythe spaces between the rows. In this embodiment, the harvesting wagonmay be disposed above or below a maintenance gangway disposed in thespace between the rows, or may form the maintenance gangway itself, withstanding areas being formed on the harvesting wagon.

According to one alternative embodiment of the present invention, theharvesting wagon is mounted to be displaceable in a region that is onthe other side of the fish tanks in relation to the spaces. In thiscase, it is possible to prevent the space between the rows from beingdoubly occupied by the harvesting wagon and the maintenance gangway, andthe harvesting wagon instead has access to the fish tanks from a sidedifferent from the space between the rows. Such configurations areparticularly suitable in the case of multi-row fish tank arrangements,whereby it should be understood in this regard that a harvesting wagoncan also be used for fish tanks that are arranged on either side of itspath of travel.

In the embodiments of the present invention that include a harvestingwagon, it is preferred when each fish tank has a closable opening in awall demarcating the fish holding section from the region in which theharvesting wagon is displaceably mounted, the opening preferably has aconnector for a harvesting line on the side facing the harvesting wagon,wherein the openings are preferably at the same height in relation tothe path of travel of the harvesting wagon, for example in relation tothe ground contact area. By providing an appropriate connector on theharvesting wagon, the harvesting wagon can thus be connected in a quickand efficient operation to the fish tank, so as to perform theharvesting operation. Since the connector moves at a constant heightwhen the harvesting wagon is moved, due to the harvesting wagon beinghorizontally movable, it is advantageous to locate the openings at amatching height as well, so that no major adjustment of the connectorneeds to be made.

It is further preferred when the wall that demarcates the fish holdingsection of a first fish tank from the region in which the harvestingwagon is displaceably mounted has a first closable opening which has aconnector for a harvesting line on the side facing the harvesting wagonand which opens into the fish holding section of the first fish tank,and a second closable opening which has a connector for a harvestingline on the side facing the harvesting wagon and which opens via apipeline into the fish holding section of the second fish tank, thefirst fish tank being disposed between the second fish tank and the areain which the harvesting wagon is displaceably mounted, and the first andsecond opening preferably being at the same height in relation to theground contact area. According to this preferred embodiment of thepresent invention, it is possible to use one harvesting wagon to harvesttwo fish tanks disposed in different rows, wherein the harvesting wagonis displaceable in a roaming space that is located immediately adjacentto one of the two tanks. The other tank is made accessible to theharvesting wagon by an appropriate pipeline which opens into a matchingopening on the side facing the roaming space of the harvesting wagon. Itshould be understood in this regard, that the first and second closableopenings are preferably configured such that closure occurs directly inthe tank wall region of the respective fish tank, in order to preventfish from being in the pipeline after the opening has been closed, andno longer being able to reach the container on the harvesting wagon. Thepipeline provided in this embodiment of the present invention may rununderneath the first fish tank, or it may run through the fish holdingsection of the first fish tank.

Another preferred embodiment of the present invention is characterizedby four horizontally adjacent rows of fish tanks extending parallel toeach other, wherein a maintenance alleyway is formed between the firstand second rows, and between the third and fourth adjacent rows, and aregion in which the harvesting wagon is displaceably mounted is disposedbetween the second and third rows, and further characterized by aplurality of openings for connecting a harvesting line, which isdisposed in the walls facing the region in which the harvesting wagon isdisplaceably mounted, wherein each fish tank has an assigned opening.With this embodiment, a particularly space-saving arrangement of fishtanks is provided which is efficient to operate. This arrangement ischaracterized in that a total of three alleyways are provided betweenthe four fish tanks, the middle one being used to move the harvestingwagon therein, and the harvesting wagon preferably being connectable forharvesting purposes to the fish tanks of all four rows of fish tanks viaappropriate pipelines. In the two outer spaces between the rows of fishtanks, appropriate maintenance walkways are provided, which allowservice operations and maintenance work to be carried out on each of thefish tanks in the four rows by virtue of the direct access thusprovided.

It is further preferred that when the fish tanks are arranged in atleast one row, the adjacent fish tanks in the row are arranged relativeto each other such that the water outlet from the sedimentation sectionof a tank opens into the water inlet of a bioreactor section of theadjacent tank, and the sedimentation section of one tank preferablyborders on the bioreactor section of the adjacent tank. According tothis preferred embodiment, the fish tanks are coupled to each other in amanner that is advantageous for water quality, in that the water circuitis guided alternately through the reactor section, the fish holdingsection, the sedimentation section, the reactor section, the fishholding section, the sedimentation section, etc. of successive tanks.

It is yet further preferred that when the fish tanks are arranged in atleast two rows, a water circuit is formed by the fish tanks of the tworows, wherein at least two pairs of fish tanks opposite each other arearranged in such a manner relative to each other:

-   -   that the water outlet from the sedimentation section of one tank        in a first row opens into the water inlet of a bioreactor        section of another tank in an adjacent row, and    -   that the water outlet of the sedimentation section of one tank        of the adjacent row preferably opens into the water inlet of the        bioreactor section of another tank in the first row.

In this way, a water circuit through at least two rows of fish tanks isformed that is beneficial for the water quality, and which simplifiesthe structure. More particularly, the respective linkage betweensedimentation sections and reactor sections may be effected in the pairsof fish tanks located at the end of each respective row, in order toform a circuit between the two rows that includes all the fish tanks.

It should be understood in this regard that it is specificallyadvantageous when the pairs also face each other in such a way that thesedimentation section of the one row lies immediately adjacent to thereactor section of the other row, so that short conduit paths can berealized.

More particularly, the fish tank according to the present invention andthe fish tank arrangement according to the present invention permit amethod for harvesting an indoor fish tank, wherein the method ischaracterized by the steps of:

-   -   connecting a harvesting tank to an opening disposed in a fish        holding section of the fish tank;    -   draining the water in the fish holding section and the fish        therein into the harvesting tank, and    -   recycling the drained water to the fish holding section,        wherein the draining and preferably the recycling of the water        is performed by the influence of gravity.

This method permits simplified and efficient harvesting, in particularunder the influence of gravity when raised fish tanks are used.

The method can preferably be carried out in such a way that theharvesting tank is disposed on a displaceable wagon that is moved to thefish tank before the fish are harvested. This facilitates transportationof the harvested fish.

These and other advantages of the invention will be further understoodand appreciated by those skilled in the art by reference to thefollowing written specification, claims and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention shall now be described withreference to the attached drawings, in which:

FIG. 1: shows a perspective view, from the side and from above, of aninventive fish tank according to a first embodiment of the presentinvention,

FIG. 2: shows a cutaway view in side elevation of the fish tank in FIG.1,

FIG. 3: shows a plan view of the fish tank in FIG. 1,

FIG. 4: shows a perspective view, from the side and from above, of aninventive fish tank according to a second embodiment of the presentinvention,

FIG. 5: shows a cutaway view in side elevation of the fish tank in FIG.4,

FIG. 6: shows a plan view of the fish tank in FIG. 4,

FIG. 7: shows a cross-sectional view of an indoor fish farm having aninventive fish tank arrangement in four rows according to the firstembodiment of the present invention,

FIG. 8: shows a plan view of the fish farm in FIG. 7, and

FIG. 9: shows a cross-sectional view of an indoor fish farm having aninventive fish tank arrangement in four rows according to the secondembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

For purposes of description herein, the terms “upper,” “lower,” “right,”“left,” “rear,” “front,” “vertical,” “horizontal,” and derivativesthereof shall relate to the invention as orientated in FIGS. 1 and 4.However, it is to be understood that the invention may assume variousalternative orientations, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions and other physical characteristics relating to theembodiments disclosed herein are not to be considered as limiting,unless the claims expressly state otherwise.

FIGS. 1-3 show a fish tank 4 according to a first embodiment of thepresent invention. The fish tank 4 comprises a bioreactor section 10, afish holding section 20 and a sedimentation section 30. The threesections 10, 20, 30 are formed in a tank 4 made in one piece and havingwall and bottom regions, and are separated by partitions. A firstpartition 11 separates the bioreactor section 10 from the fish holdingsection 20, and has a longitudinal opening 12 in its upper regionthrough which freshly treated water flows from the bioreactor section 10into the fish holding section 20. The water is treated in the bioreactorsection 10 by bubbling in fine-bubbled air from the bottom region of thebioreactor section 10 and by microbiological processes under aerobicconditions.

A second partition 31 separates the fish holding section 20 from thesedimentation section 30. In the second partition 31, an opening 32 isprovided at the level of and above the bottom of fish holding section 20through which water containing sediment flows out of the fish holdingsection 20 into the sedimentation section 30.

By virtue of this configuration, water flows out of the bioreactorsection 10 as a near-surface stream into the upper portion of fishholding section 20, where it causes circulation, as shown by the arrowsin FIG. 2.

As can be seen from FIGS. 1-3, the top third portion of sedimentationsection 30 is cubic in shape and the adjoining region therebelow tapersdownwards in a wedge shape. The solids collect at the lowest point ofthe sedimentation section 30 and can be removed from there via aseparate pipeline (not shown).

The fish holding section 20 is bounded at the bottom by a bottom region25. In the same manner, the bioreactor section 10 is bounded at thebottom by a bottom region 15. The bottom region 25 of the fish holdingsection 20 is higher than the bottom region 15 of the bioreactor section10, which is at approximately the same height as the pointed bottom, ofthe sedimentation section 30 formed by a slanting bottom region 35.

The reactor section 10, the fish holding section 20 and thesedimentation section 30 are laterally bounded by walls 16, 26, 36, 37,38, 27, 17, 18, which define a respective interior volume for receivingthe water inside the fish tank.

In relation to said interior volume of the fish tank 4, a framestructure 5 consisting of a plurality of braces is disposed outside thewalls. The braces can basically be subdivided into vertical braces 6,such as the vertical braces 40, 41, 42 provided at the corners of thetank, and horizontal braces 7, such as braces 50-56 laterally supportingthe reactor section. The braces 6, 7 are partly welded to one other andpartly bolted to one another in order to allow assembly and thereplacement of the walls bounding the fish tank and its holdingsections.

The bottom or lower ends of one row of vertical braces 6 restsabuttingly on a ground support or contact area 60, as shown by way ofexample for the bottom ends 40 a, 41 a, 42 a of vertical braces 40-42.In the illustrated examples, the entire sedimentation section 30 as wellas the entire fish holding section 20 and the entire bioreactor section10 are located above said ground contact area 60. As a result, thebottoms of these sections, more specifically bottom region 15, bottomregion 25 and the downwardly slanting bottom region 35 of sedimentationsection 30 are also at or raised above the ground contact area 60.

In FIGS. 4-6, a second embodiment of the fish tank according to thepresent invention is shown, which incorporates a number of features thefirst embodiment shown in FIGS. 1-3, and described in the foregoing, andwhich is therefore described herein only in respect of the featureswhich differ.

Instead of using a first partition between the bioreactor section 1010and the fish holding section 1020, the second embodiment (FIGS. 4-6)uses a bulkhead arrangement. The bulkhead arrangement is formed by afirst bulkhead partition 1070, a second bulkhead partition 1080 spacedapart from the first bulkhead portion 1080 and forming a water conduitshaft 1090 between the two bulkhead partitions 1070, 1080.

The first bulkhead partition 1070 separates the bioreactor section 1010from the water conduit shaft 1090 and has an opening 1071 extendingacross its entire width. The opening 1071 is disposed in the region ofthe upper water surface inside the fish tank.

The second bulkhead partition 1080 separates the water conduit shaft1090 from the fish holding section, and ends or terminates at a locationabove the bottom surface 1025 of the fish holding section 1020, thusleaving an opening 1081 that extends across the entire width of thesecond bulkhead partition 1080. The bottom of opening 1081 is formed bythe bottom surface 1025 of the fish holding section 1020, and theopening 1081 extends upwards therefrom across a limited region to thelower edge of the second bulkhead portion 1080.

By virtue of this arrangement, water discharged from the bioreactorsection 1010 is through opening 1071 channeled downwards in the waterconduit shaft 1090 and exits through opening 1081, just above the bottomsurface 1025 of the fish holding section 1020 in a stream flowingparallel to the bottom surface 1025. A circulation pattern marked by thearrows in FIG. 5 is thus formed in the fish holding section 1020, withthe circulation flowing in the direction of the sedimentation section1030 when close to the bottom, and in the direction of the bioreactorsection 1010 when close to the surface. This effects particularlyefficient removal of sediments from the fish holding section 1020 fordepositing into the sedimentation section 1030.

FIG. 7 shows a cross-sectional view of a fish tank arrangementcomprising four rows of fish tanks 100, 200, 300, 400. The two fishtanks 100, 200 on the left are arranged at such a distance from eachother that a space 150 is formed laterally between them. In said space150, a walkway 160 raised above the ground contact area 60 is formed, onwhich a user of the fish tank arrangement of FIG. 7 can move along thetwo rows of fish tanks 100, 200, and can perform service and maintenancework on the fish tanks in those rows. A space 350 is formed in asymmetrical manner between fish tank rows 300 and 400, in which space amaintenance walkway 360 is disposed. Maintenance walkways 160, 360 areformed by a catwalk grating that rests on horizontal braces connected tothe frame structure of fish tank rows 100, 200 and 300, 400.

In the central aisle 250 of the fish tank arrangement shown, that is tosay the space between fish tank rows 200 and 300, a space is providedthat is wider than spaces 150, 350. In this wider space, there isdisposed a harvesting wagon 500 which rests and travels on rollers 510,520 and rails 530, 540, respectively.

In a side wall of the fish holding section of each of the, fish tanks inrows 200 and 300 harvesting openings 210 and 310 are provided, which areformed towards the region in which the harvesting wagon 500 can bedisplaceably moved or shifted along rails 530, 540. Both openings 210,310 are at the same height.

Each of the fish tanks in the outer rows 100, 400 likewise has anopening in the side wall of the fish holding section, wherein each ofthe openings is connected via a pipeline 120, 420 to openings 130, 430,which are oriented towards the central aisle 250 in which the harvestingwagon 500 is displaceably mounted. Sections of pipeline 120, 420 rununderneath the bottom region of the fish holding section of the fishtanks in rows 200, 300.

In the example shown, openings 130, 430 are disposed at identicalheights and below openings 210, 310 of the fish tanks in rows 200 and300. The harvesting wagon 500 has connecting lines for harvesting (notshown), preferably oriented towards either side, which can be adjustedin height, and can be moved horizontally with the harvesting wagon inorder to connect the openings of all four fish tank rows.

FIG. 8 shows a plan view of an arrangement of fish tanks of the typeshown in FIG. 1, and illustrates the layout of all the fish tanksprovided therein. Each fish tank row comprises a total of 12 fish tanks101-112, 201-212, 301-312 and 401-412. The fish tanks are eachconfigured according to the embodiment shown in FIG. 1, and each has areactor section 105 a, a fish holding section 105 b and a sedimentationsection 105 c, as shown by way of example with reference to fish tank105. The fish tanks are preferably arranged end to end in each row suchthat the sedimentation section of one fish tank is directly adjacent toor adjoined by the bioreactor section of a next adjacent fish tankendwise.

Each row of fish tanks is subdivided into a left-hand group of fishtanks and a right-hand group of fish tanks. The respective left-handgroup 100 a, 200 a in fish tank row 100, 200 forms a closed,self-contained water circuit, and the left-hand groups 300 a, 400 a inrow 300, 400 likewise form a closed water circuit, as do the right-handgroups 100 b, 200 b and the right-hand groups 300 b, 400 b of rows100-400. This closed water circuit is achieved by water flowing from arespective sedimentation section of one tank in a row into thebioreactor section of an adjacent fish tank in the same row, and, in thepair of fish tanks at both ends of the left-hand and right-hand rowsections, by the water flowing from a sedimentation section of the fishtank of the one row into the bioreactor section of the tank of the otherrow.

Finally, as can be seen from FIG. 8, a central control room 600 isprovided in the building accommodating the indoor fish tank arrangement,for controlling operations and monitoring the operation of the fishtanks.

FIG. 9 shows a second embodiment of a fish tank arrangement according tothe present invention, which is identical in a number of features withthe first embodiment described in the foregoing, and which is describedherein only with regard to the features which differ.

Fish tank rows 1200 and 1300 have a harvesting opening 1210 and 1310,respectively, in the bottom region of the fish holding section. Eachharvesting opening 1210, 1310 is connected by a pipeline 1220, 1320,which is angled from an initially perpendicularly downward course by 90°into a horizontal course in the direction of the middle aisle 1250, to aconnector opening 1230, 1330 formed towards the middle aisle 1250 inwhich the harvesting wagon 1500 can be displaceably moved. The twoopenings 1230, 1330 are positioned at identical heights.

The fish tanks in the outer rows 1100, 1400 likewise have one openingeach 1110, 1410 that is formed in the bottom region of the fish holdingsection, each of said openings being connected via a pipeline 1120, 1420to openings 1130, 1430, which for their part are formed towards thecentral aisle or middle 1250 in which the harvesting wagon 1500 isdisplaceably mounted. In this case, pipelines 1120, 1420 run partlyunderneath the bottom region of the fish holding section of the fishtanks in rows 1200, 1300.

Openings 1130, 1430 are horizontally adjacent to openings 1230, 1330 ofthe fish tanks in rows 1200 and 1300, and are disposed at identicalheights with said openings 1230, 1330. Consequently, a harvestingpipeline connector which is associated with the harvesting wagon 1500can be moved horizontally with the latter, and can be moved into theregion of the respective opening of the tanks to be harvested. For thispurpose, harvesting wagon 1500 has connecting lines for harvesting (notshown), more specifically towards either side, in order to connect theopenings in all four fish tank rows to said connector.

The invention, according to one preferred embodiment, provides anecofriendly indoor fish farm. This indoor fish farm basically consistsof a building containing tanks for feeding or breeding aquaticorganisms, as well as a processing unit for the breeding water and forthe wastewater. The “internal cleaning system”, comprising an integratedunit in which the fish are kept, biological processing of the breedingwater and a sedimentation section, is used for the indoor fish farm.This contrasts with external cleaning units which process the breedingwater biologically outside the fish tank.

The indoor fish farm is composed of one to several modules and containsthe following technical components:

-   -   fish tanks (including bioreactor and sedimentation sections)    -   air pipeline network    -   wastewater network    -   compressor for process air    -   feeder units    -   wastewater treatment system    -   container for fish manure    -   control and monitoring system

The fish tank is basically designed in three parts. It consists of afish section (or fish holding section), a bioreactor section and asedimentation section. The fish holding section is located in themiddle, between the bioreactor and sedimentation sections. Thebioreactor and the sedimentation sections are each spatially demarcatedfrom the fish holding section by a partition. Sieves incorporated inthese partitions create a linkage between the units and the entirewaterbody. Functionally, however, each part must be seen as anautonomous unit to which a specific role is assigned.

The fish holding section is the part where the fish are kept. In orderto provide the fish with optimal living conditions, the water must becirculated and purified (for uniform distribution of dissolvedsubstances such as oxygen, for example). Underneath the biopack in thebioreactor, large quantities of air are injected via a special fansystem, as a result of which the water column in the biologicalpurification stage (the bioreactor) is raised. Pressure is built up inthe bioreactor due to the water being raised. In the partition betweenthe bioreactor and the fish section, there is a grating near the watersurface. The pressure generated in the bioreactor can diffuse throughthe grating, as a result of which produce a flow in the longitudinaldirection of the tank at the water surface. The flow continues in thedirection of the sedimentation section and decreases with increasingdistance from the bioreactor. The strength of flow is sufficient totransport suspended particles in the direction of the partition betweenthe sedimentation part and the fish section. At the partition of thesedimentation section, the water flow is deflected in the direction ofthe tank bottom, and from there back in the direction of the bioreactor.When the water arrives at the bioreactor, the circulation flow isre-deflected towards the surface of the water. From there, it isreplenished with new flow energy, so that circulation can recommence,and a circulatory flow is accordingly present in the tank, as shown inFIG. 2.

It is clear from the flow conditions within the tank, as describedabove, that some of the circulating water in the fish section flows pastthe grating of the sedimentation section, and hence also that part ofthe suspended particles cannot enter the sedimentation section. In orderto increase the accumulation of particles in the sedimentation section,the flow pattern of circulation can also be deflected, according to thepresent invention, in the direction of the tank bottom. This deflectionis achieved by inserting an additional bulkhead partition that ispositioned parallel to the demarcating bulkhead partition between thebioreactor section and the fish holding section. At the bottom of thisadditional bulkhead partition there is a grating through which the watercan flow. The water flows out of the bioreactor section through thenear-surface grating system of the first bulkhead partition, collideswith the additional bulkhead partition, and is deflected in thedirection of the tank bottom, where it changes direction towards thesedimentation section, flows through the fish holding section near thebottom, and directly from there through the grating in the partition toenter the sedimentation section, as shown in FIG. 5.

An important part of the indoor fish farm is the bioreactor and theaeration system. In the bioreactor, the nitrogen excreted by the fish asammonia is oxidized via nitrite to nitrate by micro-organisms(nitrification), similar to the process occurring in naturalwaterbodies. The micro-organisms colonize the substrate of the fixed-bedbioreactor and form the “biofilm”. The entire substrate unit is referredto as a “biopack”. By treating the production water biologically, thefish are thus provided with ideal growth conditions, and themicro-organisms are supplied with oxygen.

Recirculation systems are not totally closed systems. In order tocounteract the accumulation of certain substances (such as nitrate, forexample), and thus to provide optimal water conditions for the fish, apredetermined volume of water is removed from the tank and replaced byfresh water. The water renewal rate, including evaporation, is betweenfive and ten percent per day. Daily removal of water is primarilyattributable to the removal of sludge produced by fish excrement anduneaten feed. Suspended particles are kept suspended in the fish sectionby the circulation flow initiated by the bioreactor and produced nearthe water surface. The fish excrement and feed remnants pass from thefish section into the sedimentation section by suction force via agrating at the bottom of the fish section. This suction force isproduced by a mammoth or large pump which pumps water out of thesedimentation section into a bypass. The bypass is used for connectingand for exchanging water with the adjacent tanks. The excrement and feedremnants accumulate in the funnels of this third functional unit andevery two hours are automatically transferred pneumatically from thefunnels of the sedimentation units to the wastewater treatment system bymammoth pumps. The sedimented fish manure is pumped out of this systeminto a large storage container and can subsequently be spread asfertilizer on land. By flowing through an aerobic and an anaerobicbiological chamber, the discharge water is purified and can be releasedto a receiving water or maturation pond, or can drain into the municipalsewer system.

The process air can be supplied by rotary piston compressors located inthe plant room. Depending on the size of the farm, at least one or morerotary piston compressors bear the basic load. One compressor with thesame power rating is available on standby to supply the farm with air inthe event of plant failure. All production control, monitoring anddocumentation with preset operating parameters, in-built alarm systemand production comparisons is carried out with the aid of a computerprogram.

In the foregoing description, it will be readily appreciated by thoseskilled in the art that modifications may be made to the inventionwithout departing from the concepts disclosed herein. Such modificationsare to be considered as included in the following claims, unless theseclaims by their language expressly state otherwise.

The invention claimed is:
 1. An indoor fish tank, comprising: aplurality of walls and a plurality of bottoms interconnected to define atank container having: a fish holding section for fish agriculture; asedimentation section for removal of solids by a separate pipeline, thesedimentation section having at least one opening communicating withsaid fish holding section in such a way that water from a bottom regionof said fish holding section flows out of said fish holding section intosaid sedimentation section; a bioreactor section bubbling fine-bubbledair therein having at least one opening communicating with said fishholding section in such a way that water from a region close to theupper surface of said bioreactor section flows out of said bioreactorsection into said fish holding section; a frame structure having: aground contact portion which abuttingly supports said frame structure ona support surface, and being connected with said walls and said bottomsof said tank container in such a way that the bottom of said fishholding section is disposed above said ground contact portion of saidframe; and a plurality of braces which rest against outer surfaces ofsaid walls and said bottoms of said tank container and support the sameagainst the static pressure exerted by the water held in said tankcontainer.
 2. An indoor fish tank as set forth in claim 1, wherein: saidsedimentation section has a bottom disposed above said ground contactportion of said frame structure.
 3. An indoor fish tank as set forth inclaim 2, wherein: said bioreactor section has a bottom disposed abovesaid ground contact portion of said frame structure.
 4. An indoor fishtank as set forth in claim 1, including: a closable opening formed in awall bounding said fish holding section, and having a connector forattaching thereto one end of a harvesting line disposed outside of saidtank container.
 5. An indoor fish tank as set forth in claim 1, wherein:said fish holding section is disposed geometrically between saidbioreactor section and said sedimentation section.
 6. An indoor fishtank as set forth in claim 1, including: a flow shaft positioned betweensaid bioreactor section and said fish holding section, and beingseparated from said bioreactor section by a first bulkhead partitionwhich has an opening in a top portion thereof, and which is separatedfrom said fish holding section by a second bulkhead partition which hasan opening in a lower portion thereof, with a lower boundary edge ofsaid opening disposed level with the bottom of said fish holdingsection.
 7. An indoor fish tank as set forth in claim 1, including: atleast one pair of said fish tanks arranged in relation to each othersuch that facing walls of said fish holding sections of said two fishtanks define a space therebetween; and a maintenance walkway disposed insaid space at such a height that a person standing on said maintenancewalkway can reach into both of said fish holding sections from above. 8.An indoor fish tank as set forth in claim 7, comprising: a plurality offish tank pairs arranged relative to each other such that said spacesbetween said fish tank pairs form a maintenance alleyway; and amaintenance gangway formed by said maintenance walkways.
 9. An indoorfish tank as set forth in claim 8, comprising: a harvesting wagonmounted to be displaceable in an axial direction of said maintenancegangway and having a container for receiving fish therein which isconnectable to said harvesting opening of said fish tanks by aharvesting line.
 10. An indoor fish tank as set forth in claim 9,wherein: said harvesting wagon is mounted to be displaceable on railsextending in the axial direction of said maintenance gangway, whichareas supported on said frame structure of said fish tank.
 11. An indoorfish tank as set forth in claim 10, wherein: said harvesting wagon ismounted to be displaceable in the region formed by said spaces betweensaid rows.
 12. An indoor fish tank as set forth in claim 10, wherein:said harvesting wagon is mounted to be displaceable in a region that ison the other side of the fish tanks in relation to said spaces.
 13. Anindoor fish tank as set forth in claim 9, wherein: each said fish tankhas a closable opening in a wall thereof associated with said fishholding section and oriented toward said harvesting wagon, whichincludes a connector for attaching a harvesting line onto saidharvesting wagon.
 14. An indoor fish tank as set forth in claim 9,including: four horizontally adjacent rows of said fish tanks extendingparallel to each other, wherein a maintenance alleyway is formed betweenfirst and second and between third and fourth adjacent rows, and aregion in which said harvesting wagon is displaceably mounted isdisposed between said second and third rows; a plurality of openings forconnecting a harvesting line, which are disposed in the walls facingsaid region in which said harvesting wagon is displaceably mounted,wherein each said fish tank is assigned an opening and said openings arearranged horizontally at the same height.
 15. An indoor fish tank as setforth in claim 8, wherein: said fish holding section of a first one ofthe fish tanks includes: a first closable opening having a connector fora harvesting line on the side facing said harvesting wagon and whichopens into the said holding section of said one fish tank; and a secondclosable opening having a connector for a harvesting line on the sidefacing said harvesting wagon and which opens via a pipeline into saidfish holding section of a second one of said fish tanks; and whereinsaid first fish tank is disposed between said second fish tank and thearea in which said harvesting wagon is displaceably mounted, and saidfirst and second openings are at the same height in relation to saidground contact area.
 16. An indoor fish tank as set forth in claim 1,wherein: said fish tanks are arranged in at least one row, whereinadjacent fish tanks in the row are arranged relative to each other suchthat the water outlet from said sedimentation section of a first one ofsaid tank container opens into the water inlet of said bioreactorsection of said adjacent tank containers, and said sedimentation sectionof said first tank container borders on said bioreactor section of anadjacent tank container.
 17. An indoor fish tank as set forth in claim1, including: a plurality of said fish tanks arranged in at least tworows with a water circuit is formed by said fish tanks of the at leastsaid two rows, wherein at least two pairs of said fish tanks oppositeeach other are arranged in such a manner relative to each other,wherein: a water outlet from said sedimentation section of one tank in afirst row opens into a water inlet of a bioreactor section of one tankin an adjacent row; and a water outlet of said sedimentation section ofone tank of the adjacent row opens into a water inlet of the bioreactorsection of one tank in the first row.